The National Toxicology Program, a federal health agency, acknowledged for the first time in April that a chemical found in thousands of plastic products, including water bottles, is of “some concern.”
The chemical, bisphenol A (BPA), is known to be an “endocrine disruptor.” It has hormonelike effects that could potentially increase the risk for breast and prostate cancers. Studies indicate that it also might be linked to miscarriages, early puberty in girls and birth defects.
To learn more about the effects of plastics on foods and beverages, Bottom Line/Personal spoke with Patricia Hunt, PhD, a noted reproductive biologist and geneticist at Washington State University…
What types of products contain BPA?
BPA, or chemicals that might have similar effects (such as phthalates), are found in some sports bottles, as well as some baby bottles, food wraps and storage containers. BPA also is used in the resins that coat the insides of many food and beverage cans. In addition, it is in a variety of plastic products, such as compact discs and eyeglass lenses.
How dangerous is it?
Traditionally, the potential danger of a chemical has been assessed in dose response studies — this assumes that the higher the dose, the greater the risk. Thus small amounts usually are not cause for alarm.
BPA is different because it has powerful, hormonelike effects. Like the body’s natural hormones, even trace amounts can produce profound changes in the body.
We entered into this area of research purely by accident. We were studying eggs from normal female mice when we suddenly noticed a huge increase in abnormalities. It turned out that our laboratory mice were being exposed to BPA — because their plastic cages and water bottles had been inadvertently damaged when they were washed with the wrong detergent.
About 10% of their eggs were chromosomally abnormal. (In mice not exposed to BPA, only 1% of eggs were abnormal.)
It’s not yet known if humans exposed to BPA face similar threats. We suspect that they do. We do know that phthalates, chemicals that make plastics soft and pliable, have been linked to genital defects in newborn boys.
Exposure to chemicals such as BPA and phthalates that have hormonelike effects hasn’t been conclusively shown to cause cancer. But the evidence is getting stronger that they might cause a variety of cancers or reproductive system abnormalities, including polycystic ovary disease.
Infants (and fetuses) face the highest risks from these chemicals because their brains and reproductive tracts are still developing. A bill was introduced in the Senate to ban BPA from all products intended for babies, including baby bottles.
How much BPA is safe?
No one knows. The Environmental Protection Agency has estimated that an exposure of up to 50 micrograms (mcg) of BPA per kilogram of body weight per day is safe. But that calculation is based on older animal studies, and more recent studies suggest that much lower levels of BPA — as little as 0.025 mcg per kilogram of weight — induce a variety of adverse effects in rats and mice.
Researchers from the Centers for Disease Control and Prevention analyzed urine samples from 2,517 Americans six years of age and older. They found traces of BPA in nearly 93% of the population.
Which products contain BPA?
It’s hard to know. Some plastic containers are stamped with recycling codes that indicate the type of plastic used, but recycling codes are only a partial guide. For example, polycarbonate plastic — which contains BPA — doesn’t have a specific recycling code. If it is coded, it will be stamped with the number “7.” But this is the code for “mixed plastics,” so seeing a “7” doesn’t tell you for certain that the product contains BPA.
Some plastics are considered safer than others because they don’t react as readily to heat or harsh cleaners. These include high-density polyethylene (used in milk and water jugs and marked “2”)… low-density polyethylene (used in produce bags and some food storage containers, and marked “4”)… and polypropylene (used in yogurt containers and some food storage containers and marked “5”).
I’m not sure what to say about polyethylene terephthalate (commonly abbreviated PET and marked with the number “1”). It is better than polycarbonate, but there is some concern that it may leach antimony trioxide (a heavy metal used in the production of plastic).
Should we stop using disposable water bottles?
Many people already have. I have switched to Klean Kanteen stainless steel containers when I want to take water with me (530-345-3275, www.kleankanteen.com). Nalgene, an outdoor-products company that makes refillable bottles, already has phased out polycarbonates — the company now produces sports bottles from polymers that don’t contain BPA (800-625-4327, www.nalgene-outdoor.com). Other companies also will be introducing BPA-free plastics in the months or years to come.
If you like to take water with you and prefer lightweight plastics, look for those made with polyethylene or polypropylene — or that say “BPA-free” on the label.
Is it safe to microwave food in plastic containers or plastic wraps?
I’m not certain that anyone can tell you whether or not it is “safe.” I can tell you that I don’t do it. Heat is an invitation for chemicals to migrate out of plastic. We’ve all noticed the “plastic-y” taste that is sometimes present when we microwave foods in take-out containers or some storage containers. What we’re tasting is chemicals. My rule at home is that plastics never go in the microwave. I also throw out any plastic items that are showing signs of wear.
What about washing plastic containers?
Wash them by hand, and use only a mild dishwashing solution. The heat in many dishwashers is too hot for plastics — it accelerates the rate at which they break down and release chemicals. Strong detergents also can cause plastics to release more chemicals.
Should we avoid canned foods?
Unfortunately, consumers can’t know which products contain BPA, and for most people, it’s unrealistic to give up all canned foods.
Be aware that once foods are canned, they’re often subjected to high-heat sterilization. If a can is lined with a BPA-containing resin, the heat will cause more BPA to leach into the food. This means that canned foods might contain more BPA than, say, canned sodas. But this is just speculative at this point. In my opinion, consumers should demand that information about the lining be disclosed on the can label.
What about baby bottles?
Formula fed babies are potentially exposed to a lot of BPA. It’s present in some baby bottles and in the linings of liquid and powdered formula containers. Federal officials have started asking manufacturers if they test routinely for BPA, but this is all very recent.
Right now, the best choices are baby bottles made from glass or BPA-free plastic, such as BornFree bottles.
Are other plastics a risk?
We don’t know. BPA is present in all sorts of plastics, including swing seats and PVC plumbing. The assumption has been that our main exposure to BPA is from foods and beverages. However, a new study suggests that foods alone can’t account for the BPA levels in the US population.
It’s possible — but not certain — that we absorb BPA through the skin from environmental exposure, such as dust or via bathwater that has traveled through PVC pipes.
